This invention relates to a process for producing a diamond-like film and an apparatus therefor, and more specifically to a process and an apparatus for producing a diamond-like film with a high degree of film-forming efficiency. The term "diamond-like film" used herein means to include a diamond or diamond-like film which is at least very close in crystal structure to genuine diamond. The degree of crystalization depends on the process conditions.
Many different processes have hitherto been proposed for the manufacture of diamond or diamond-like carbon films. However, difficulties have been involved in forming films of adequately high crystallinity, close to that of natural diamond crystals. The prior art processes include one (called ionization evaporation) which consists of ionizing a lower hydrocarbon gas such as methane gas by arc discharge or other ionizing means to form an ion stream and then accelerating the flow by the application of an electric field and directing it toward a substrate on which to form an objective film. The process is known for high film-forming efficiency and for the excellence of the resulting diamond-like film, with such good surface properties, high hardness, great heat conductivity, and high refractive index that no surface finish treatment is necessary.
The weak point of the conventional processes that depend on ionization, such as ionization evaporation, for the formation of a diamond-like film is slowness, the film-forming rate being usually of the order of 5.mu.m per hour. Improvements in this respect are essential for the commerical acceptance of these processes. Further, it would be desirable if the efficiency of electric power consumption per unit thickness of the film were enhanced and the film-forming rate increased without any change in the properties of the diamond-like film.